48 CFR §1817.7000

1. (a)Down-selection. In a phased acquisition, the process of selecting contractors for later phases from among the preceding phase contractors.
2. (b)Phased Acquisition. An incremental acquisition implementation comprised of several distinct phases where the realization of program/project objectives requires a planned, sequential acquisition of each phase. The phases may be acquired separately, in combination, or through a down-selection strategy.
3. (c)Progressive Competition. A type of down-selection strategy for a phased acquisition. In this method, a single solicitation is issued for all phases of the program. The initial phase contracts are awarded, and the contractors for subsequent phases are expected to be chosen through a down-selection from among the preceding phase contractors. In each phase, progressively fewer contracts are awarded until a single contractor is chosen for the final phase. Normally, all down-selections are accomplished without issuance of a new, formal solicitation.